Transformer cooling system



E. D. TREANOR TRANSFORMER COOLING SYSTEM Feb. 3, 1959 2 Sheets-Sheet l Filed NOV. 29, 1955 Feb. 3, 1959 E. D. TREANoR 2,872,651

TRANSFORMER COOLING SYSTEM Filed Nov. 29, 1955 2 Sheets-Sheet 2 lnited States hat-cnt O TRANSFORh/IER COLING SYSTEM Edward D. Treanor, Athens, Ga., assignor to General Electric Company, a corporation of New York Application November 29, 1955, Serial No. 549,729

8 Claims. (Cl. 336-58) This invention relates to a cooling system, and more particularly to a cooling system for electrical transformers.

In one prior art form of electrical transformer both the magnetic core and the electrical coils are submerged within an electrical insulating liquid inside a tank. The tank is almost completely filled with said liquid except for an inert gas space in the upper portion thereof to provide for volumetric expansion of said liquid. Said liquid besides serving the function of an insulating medium for the coils also serves as a cooling medium for the core and coils by aiding in the transfer of heat by conduction and convection from the core and coils to the tank surface or radiators and thence to the ambient air.

It will be appreciated that such a large quantity of liquid increases the total cost, size and weight of the electrical transformer. Additionally, in those installations where the liquid is tiammable the fire hazards are increased by the presence of such a large quantity of liquid in the event an explosion and rupture of the tank should occur.

The electrical industry is ever seeking ways to increase the cooling eiciency of electrical transformers while simultaneously reducing their cost, size, weight and tire hazard.

Acco-rdingly, it is an object of this invention to provide an electrical transformer having an increased cooling efliciency and reduced cost, size, weight and lire hazard j over prior art electrical transformers.

It is a further object of this invention to provide an eflicient, low cost, and reduced size and weight cooling system.

ln my invention the main transformer tank is not filled with insulating liquid as has been the practice heretofore, and only the electrical coils or windings are submerged in insulating liquid. This liquid, which removes heat from the coils, dissipates its heat to the ambient air in a radiator provided by making the sides of the tank double walled. This arrangement results in el'licient cooling since the liquid upon becoming heated by the coils is directly moved to and rapidly circulated through the radiator. A reduction in cost, size and weight is achieved since less liquid is used than has been the prior practice. Also, in those installations where flammable liquids are used the chances of a spreading tire attendant to an explosion Within the liquid is reduced due to the reduced quantity thereof.

In the drawings, Fig. 1 is a partly broken away side elevation view of one form of my invention, and Fig. 2 is a sectional View of the same form of the invention,

, said sectional view being taken along the line 2 2 of Fig. l. Fig. 3 is a partly broken away side elevation view of a second form of my invention, and Fig. 4 is a similar view of a third form of my invention. Like reference numerals will be used throughout the various figures to indicate similar parts.

iiatented Feb.

Referring now particularly to Figs. 1 and 2 of the drawings, shown therein is a stationary electrical induction apparatus or transformer comprising a tank 1 having a magnetic core and electrical windings or coils positioned therein. The core comprises two generally rectangular magnetic strip material wound core loops 2 which abut each other at one of their longer sides to provide a three-legged magnetic core. The core loops 2 are held in their illustrated assembled relationship by horizontal and vertical core braces 2.' and 2 respectively which are Welded or bolted together. The electrical windings or coils comprise low and high voltage winding or coil sections 3 and 4 respectively which are linked with respect to the central leg of the core. The windings are enclosed within a generally annular electrical insulating material housing or jacket 5. In assembling the core and windings together the windings are first positioned in the jacket 5 and then the jacket is slipped down on the central leg of the core. The upper right-hand corner of the left-hand loop 2 and the upper left-hand corner of the right-hand loop 2 can have butt joints formed therein whereby both loops can be hinged open to facilitate linking of the jacketed windings with the central leg of the core. This expedient is well known in the art, and it will be equally obvious to those skilled in the art that the particular transformer construction shown is illustrative only of the invention and that many other forms of transformers can be used.

The sides of the tank 1 are provided with a radiator by connecting the top and bottom of a cylindrical member 6 to the side wall of tank 1 as by welding. The side wall of tank 1 and the spaced member 6 together define a generally annular radiator which is in communication with the annular jacket 5 at top and bottom by conduits 7 and S respectively. It will be obvious that other forms of radiators could be mounted on the tank 1. For instance, the conduits 7 and 8 could be connected to exterior vertically extending radiator tubes carried by the tank 1. However, the illustrated 'form of radiator is preferred inasmuch as it is low cost and easily assembled, and provides large heat radiating surfaces to the ambient air. The top of the jacket 5 is closed by a cover 5 and the top and bottom of tank 1 are closed by end covers 9 and 10 respectively. Extending from cover 5' are a pair of low voltage leads 11 which are connected to a pair of low voltage side wall mounted bushings 12, and a pair of high voltage leads 13 which are connected to a pair of high voltage bushings 14 mounted on cover 9.

The radiator defined by the side walls of tank 1 and member 6, the jacket 5, and the conduits '7 and 8 is a sealed liquid system which is filled with an electrical insulating liquid 15. Also, the radiator has an expansion chamber 16 connected thereto to provide for volumetric expansion of liquid 15. As is well known in the art axially parallel extending spacers 17 are utilized in the windings to provide axially parallel extending cooling ducts. When the transformer is in operation the heated liquid in the jacket 5 rapidly rises in the narrow axially parallel extending winding cooling ducts and then is directly and rapidly carried by the conduits to the upper end of the tank radiator. ln the narrow tank radiator the heated liquid is cooled by the ambient air and rapidly travels down through the radiator and thence through the conduits 8 back to the bottom of the jacket 5 for another cooling cycle.

The tank 1 is also sealed at top and bottom and is filled with an inert gas. The magnetic core of the transformer is in part cooled by the liquid 15 inasmuch as the core and jacket 5 are closely adjacent each other. Heat is also dissipated from the core to the tank 1 by radiation, conduction and natural convection of the inert gas within tank 1. In the event liquid 15 is flammable there is less danger of spreading fire should an explo-sion occur within the iiquid l5 due to breakdown of the electrical insulation ofhthe coils or the like. .For .instance, if an explosion occurswithin jacket' 5 andshduld jacket 5 be ruptured Vthere is very little Aprobability that the liquid l5 will spread beyond tank il. Thatis, due' to the small quantity of liquid l5 involved the probability is that tank 1 will not burst but that the liquid will be confined to tank l and the arc or arc' products will beY extinguished due to the blanketingleiect of thev inert gas within tank i.

The form of the invention illustratedV in Fig. 3 isrsimilar to that of Figs. l and 2 except that the interior 'of tank 1 is vented to the ambient air to take advantage of the largeY heat dissipating surface presented by the memberr 6. The bottom tank cover of Fig. l has been replaced by a pan lid. The pan i9 is circular and has a smaller radius thanl the tank 1 so that the ambient air can enter therebetween into the tank l. The high voltage bushings 14 are now mounted on the tank side walls to provide space for a rotary shield 2d cooperative with a vent'opening 2i provided in an upper tank'cover 9'. The shield has one or more vanes 22 thereon, communicates with opening 2i, and is vented to the atmosphere. A support member 23 which does not close the opening 2i has a vertical shaft 24 thereon upon which the shield 26' is rotatably mounted. Such opening of the bottom and top of tank ll provides natural circulation of the ambient air upwardly through the interior of tank il' to remove heat directly from the magnetic core and the largeA interior'heat dissipating surface of member '6. The volume of pan l0 is made large enough to catch allof the liquid in jacket 5 in the event an Y electrical ,areYV should occur therein and cause rupture of the'- jacket v5. It will beV appreciated that some insulatingj liquids Yare quite expensive yso beside reducing costs Vby reducing the necessary quantity thereof it is also desirable to be able to catch and reclaim the same in the event' of rupture of jacket 5.

The form of invention illustrated in Fig. 4 is similar to thatl of Fig. 3 except that a vaporizable insulating liquid 15 which has a boiling point temperature within the normal operating temperature range of the transformer windings is utilized. The liquid l5 completely iillsl the jacket 5 but only partially or about halt fills the radiator defined by the side wall of the tank 1 and the member 6. The volume of expansion chamber 16 kis somewhat larger than that of chamber i6 of Fig. l

to ensure that there is no dangerous pressure buildup in the sealed system due to the vapors evolved from liquid 15'; Thefconduits 7' which interconnect the upper end of jacket 5 and the radiator preferably communicate with the radiator at a location just above the surface level of liquid l5', however it will be obvious that conduits `7 could connect with the radiator at the surface level of the liquid i5' in the radiator or somewhat below `said tem comprising the non-liquid filled parts of conduits 7',

the radiator, and the expansion chamber i'is filled with Y askarels canY be used.

tric strength gas which will not condense within the normal operating temperature range of the transformer and have no deleterious ettect on the insulating liquid. Two such gases are nitrogen and sulphur hexauoride. In the Fig. 4 form of the invention inert gas is used above the insulating liquid to maintain initial pressure to provide initial dielectric strength within the windings when the transformer is relatively cold. However, it may be possible to attain such initial pressure only from the vapors of the insulating liquid in which event the inert gas could be omitted. In therFigs. 1 and 3 forms of the invention conventional insulating liquids such as In the Fig. 4 form of the invention liquids such as iiuorocarbons can be used, which are characterized by boiling point temperatures within the normal operating temperature range of electrical windings of many conventional transformers. Of course, it is preferred that both the inert gases and the insulating liquids be non-fiammable, which is true of the specificv examples given.

The jacket 5 and cover 5y can be made from a wide variety of electrical insulating materials. For instance,

a glass reinforced polyester resin will provide the neceseV Vof? the high voltage winding section 4. Also, it is pos sible to make the jacket 5 and cover 5 from metal pro-L vided insulated joints are utilized so that jacket 5 and cover 5 do not constitute a short circuited turn around I the central leg of the magnetic core.

While there have been shown and described particular embodiments of the invention, it will be obvious to those Y surface level. The remaining portion of the sealed sys- 'Y the liquid vapors will rise in the conduitsV 7 and theV Y radiator and force the inert gas within conduits 7 and the radiator into the expansion chamber i6'. When the liquid vapors Contact the surfaces of the side wall of tankl and the member d they wili condense and then gradually settle to the bottom of the radiator while they are further cooled and then pass through conduits 8 back into the bottom of yjacket dior another coolingcycle. Thus, in the Fig. 4 form of the invention, the double walled tank construction will dissipate heat in part as a condenser oi the vaporized liquid, land in part by natural convection of the; liquid. Y

vBy an inert gas is meant,anondiammablehigh dielec skilled in the art that changes andrnodifications may be madel without departing from the invention, and therefore 'it isV intended by the appended claims to cover all s as fall within the true such changes and modincation spirit and scope of the invention.

What I claim as new and Vdesire to secure byL-etters Patent of the United States is:

l. A stationary electrical induction apparatus comf.

is filled with electrical insulating'liquid, said tank being filled with a gas Awhich contacts said core, the sides of, said tank being double walled and defining a radiator,`

and conduits connecting the upper and lower partsl of said container with said radiator. Y

- 2. A stationary electrical induction apparatusfcomprising a sealed main tank having a magnetic core and mechanically linked electrical windings therein, only said electrical windings being housed within a jacket which isY filledV with electrical insulatingV liquid, said tank beingl filled with an electrical insulating gas which contacts said core, the sides of said tank being double walled and de-y fining a radiator, and conduits connecting the upper and lower parts of said jacket with said radiator.

Y 3. A stationary electrical induction apparatus comprising a main tank having a magnetic core and me-` below saidV container and having a volume in excess ofV the volume of said liquid. Y

4. A stationary electrical induction apparatus comprising la main tank havinga magneticrcore and mechanically linked electrical windings therein, only said electrical -windings being housed withina containerwhich is lilled with electrical insulating liquid,` the sidesofsaidl tank being double walled and defining a radiator, conduits connecting the upper and lower parts of said container with said radiator, and opposite ends of said tank being vented to the ambient air whereby a draft of ambient air will flow through said tank and contact said core and the inner surfaces of said radiator.

5. A stationary electrical induction appa-ratus comprising a main tank having a magnetic core and mechanically linked electrical windings therein, only said electrical windings being housed within a container which is filled with electrical insulating liquid, an open receptacle positioned below said container having a volume in excess of the volume of said insulating liquid, the sides of said tank being double walled and defining a radiator, conduits connecting the upper and lower parts of said container with said radiator, and opposite ends of said tank being vented to the ambient air whereby a draft of ambient air will flow through said tank and contact said core and the inner surfaces of said radiator.

6. A stationary electrical induction apparatus cornprising a main tank having a magnetic core and mechanically linked electrical windings therein, only said electrical windings being housed within a container which' is filled with electrical insulating liquid, the sides of said tank being double walled and defining a radiator, conduits connecting the opposite ends of said container with the opposite ends of said radiator, and the opposite ends of said tank being vented to the ambient air whereby a draft of ambient air will flow through said tank and contact said core and the inner surfaces of said radiator.

7. A stationary electrical induction apparatus comprising a main tank having a magnetic core and mechanically linked electrical windings therein, only said electrical windings being housed within a container which is lled with electrical insulating liquid, said tank being lled with a gas which contacts said core, the sides of said tank being double walled and defining a radiator, conduits connecting the opposite ends of said container' with said radiator, and said liquid having a boiling point within the normal operating temperature range of said electrical windings.

8. A stationary electrical induction apparatus comprising a main tank having a magnetic core and mechanically linked electrical windings therein, only said electrical windings being housed within a container which is filled with electrical insulating liquid, said tank being lilled with a gas which contacts said core, the sides of said tank being double walled and dening a radiator, said radiator being partially filled with said liquid and the bottom of said container communicating with the bottom of said radiator and the top of said container communieating with said radiator adjacent the surface level of said liquid within said radiator, and said liquid having a boiling point within the normal operatng temperature range of said windings.

References Cited in the ile of this patent UNITED STATES PATENTS 516,850 Thomson Mar. 20, 1894 1,232,834 Nichols July 10, 1917 2,295,414 Monroe Sept. 8, 1942 2,561,738 Hill July 24, 1951 2,632,041 Bilodeau Mar. 17, 1953 FOREIGN PATENTS 216,052 Switzerland Nov. 17, 1941 

